/*
 * SHA1 hash implementation and interface functions
 * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "sha1.h"
#include "crypto.h"


/**
 * hmac_sha1_vector - HMAC-SHA1 over data vector (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @num_elem: Number of elements in the data vector
 * @addr: Pointers to the data areas
 * @len: Lengths of the data blocks
 * @mac: Buffer for the hash (20 bytes)
 * Returns: 0 on success, -1 on failure
 */
int hmac_sha1_vector(const u8 *key, size_t key_len, size_t num_elem,
        const u8 *addr[], const size_t *len, u8 *mac)
{
    unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
    unsigned char tk[20];
    const u8 *_addr[6];
    size_t _len[6], i;

    if (num_elem > 5) {
        /*
         * Fixed limit on the number of fragments to avoid having to
         * allocate memory (which could fail).
         */
        return -1;
    }

    /* if key is longer than 64 bytes reset it to key = SHA1(key) */
    if (key_len > 64) {
        if (sha1_vector(1, &key, &key_len, tk))
            return -1;
        key = tk;
        key_len = 20;
    }

    /* the HMAC_SHA1 transform looks like:
     *
     * SHA1(K XOR opad, SHA1(K XOR ipad, text))
     *
     * where K is an n byte key
     * ipad is the byte 0x36 repeated 64 times
     * opad is the byte 0x5c repeated 64 times
     * and text is the data being protected */

    /* start out by storing key in ipad */
    os_memset(k_pad, 0, sizeof(k_pad));
    os_memcpy(k_pad, key, key_len);
    /* XOR key with ipad values */
    for (i = 0; i < 64; i++)
        k_pad[i] ^= 0x36;

    /* perform inner SHA1 */
    _addr[0] = k_pad;
    _len[0] = 64;
    for (i = 0; i < num_elem; i++) {
        _addr[i + 1] = addr[i];
        _len[i + 1] = len[i];
    }
    if (sha1_vector(1 + num_elem, _addr, _len, mac))
        return -1;

    os_memset(k_pad, 0, sizeof(k_pad));
    os_memcpy(k_pad, key, key_len);
    /* XOR key with opad values */
    for (i = 0; i < 64; i++)
        k_pad[i] ^= 0x5c;

    /* perform outer SHA1 */
    _addr[0] = k_pad;
    _len[0] = 64;
    _addr[1] = mac;
    _len[1] = SHA1_MAC_LEN;
    return sha1_vector(2, _addr, _len, mac);
}


/**
 * hmac_sha1 - HMAC-SHA1 over data buffer (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @data: Pointers to the data area
 * @data_len: Length of the data area
 * @mac: Buffer for the hash (20 bytes)
 * Returns: 0 on success, -1 of failure
 */
int hmac_sha1(const u8 *key, size_t key_len, const u8 *data, size_t data_len,
        u8 *mac)
{
    return hmac_sha1_vector(key, key_len, 1, &data, &data_len, mac);
}


/**
 * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
 * @key: Key for PRF
 * @key_len: Length of the key in bytes
 * @label: A unique label for each purpose of the PRF
 * @data: Extra data to bind into the key
 * @data_len: Length of the data
 * @buf: Buffer for the generated pseudo-random key
 * @buf_len: Number of bytes of key to generate
 * Returns: 0 on success, -1 of failure
 *
 * This function is used to derive new, cryptographically separate keys from a
 * given key (e.g., PMK in IEEE 802.11i).
 */
int sha1_prf(const u8 *key, size_t key_len, const char *label,
        const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
{
    u8 counter = 0;
    size_t pos, plen;
    u8 hash[SHA1_MAC_LEN];
    size_t label_len = os_strlen(label) + 1;
    const unsigned char *addr[3];
    size_t len[3];

    addr[0] = (u8 *) label;
    len[0] = label_len;
    addr[1] = data;
    len[1] = data_len;
    addr[2] = &counter;
    len[2] = 1;

    pos = 0;
    while (pos < buf_len) {
        plen = buf_len - pos;
        if (plen >= SHA1_MAC_LEN) {
            if (hmac_sha1_vector(key, key_len, 3, addr, len,
                        &buf[pos]))
                return -1;
            pos += SHA1_MAC_LEN;
        } else {
            if (hmac_sha1_vector(key, key_len, 3, addr, len,
                        hash))
                return -1;
            os_memcpy(&buf[pos], hash, plen);
            break;
        }
        counter++;
    }

    return 0;
}
